Search for

powered by FreeFind
Batteries/Lithium-ion Safety 0511117
Tracking Lithium-ion Safety Problems? - to Battery Manufacturers? - in China?
 (Feb 2006) Sandia National Laboratory researches Lithium-ion batteries for Freedom CAR program. . Sandia is researching  ways to make Lithium-ion batteries work longer and safer for possible use in hybrid vehicles in the next five to ten years.  Dan Doughty, manager of Sandia’s Advanced Power Sources Research and Development Department, said,  “Batteries are a necessary part of hybrid electric-gasoline powered vehicles and someday, when the technology matures, will be part of hybrid electric-hydrogen fuel cell-powered vehicles.”  He also noted that a safe Lithium-ion battery would be a better option for hybrids than Nickel-metal hydride because  Lithium-ion has two to three times the energy density of Nickel-metal hydride  and it has the potential to become one of the lowest-cost battery systems.  

Sandia’s Freedom CAR program centers on the areas of battery abuse tolerance and accelerated lifetime prediction.

Abuse tolerance - The technical goal is to comprehend mechanisms that lead to poor abuse tolerance, including heat-and gas- generating reactions.  Understanding the chemical response to abuse can point the way to better battery materials.  But, Doughty says, there is no “magic bullet” for completely stable Lithium-ion cells. “Fixing the problem will come from informed choices on improved cell materials, additives, and cell design, as well as good engineering practices.”  Work in abuse tolerance is beginning  to shed light on mechanisms that control cell response, including effects of the anode and cathode, electrolyte breakdown and battery additives.

Improved abuse test procedures developed at Sandia have led to Lithium-ion standards that the battery team has developed and recently published .  Doughty anticipates that the Society of Automotive Engineers will soon adopt these test procedures as national standards, just as they adopted in 1999 the abuse test procedures Sandia developed for electric vehicle batteries.

Accelerated life test - Sandia is working on developing a method to predict Lithium-ion battery life.  “We have two approaches in our research - the empirical model and the mechanic model,” Doughty says.  “The empirical model generates life prediction from accelerated degradation test data, while the mechanistic model relates life prediction to changes in battery materials.  Our approach provides an independent measure of battery life so we don’t have to rely on what battery manufacturers tell us.”  
 Fijitsu-Siemens,  Europe’s largest computer maker, recalls 250,000 notebook batteries in mid-June.  Four reports have  been received on batteries overheating.  The company has not named the manufacturer of the batteries.( BD note: Why not?)  For details on battery exchange see
More heat for Lithium-ion batteries
 Safer Electrolytes for Lithium-ion Cells
Blending low flammability liquid oligomers and polymers with ethylene carbonate have been found to produce cells which are either nonflammable or self extinguishing. Their conductivity is about 2 mS/cm and will function down to temperatures of minus 5 degrees C.  They are not suitable for high charge and discharge rates.
NASA Tech Briefs
June 2004, p.  52
 Building safer LiIon batteries
An argument is made for considering replacement of the cobalt oxide cathode material with iron phosphate materials.  One reason is that overcharge can lead to thermal runaway because 50 percent of the lithium remains in the fully discharged cobalt oxide cathode. Even construction with manganese oxide, while expanding the safety envelope, offers safety concerns. Secondary reasons include the availability of cobalt oxide and incomplete environmental impacts.

Replacing the cobalt oxide with a phosphate such as iron phosphate leads to greater stabilization. Extensive heating demands, greater than 800 degrees C, are required for decomposition.

Cobalt oxide cells experience swelling with discharge which inherently changes the structural integrity and safety of the cell.  Conversely, the iron phosphate causes no structural modification in discharge such that a fully discharged cell retains both dimensional and structural integrity, again contributing to overall safety.

Lithium-ion iron phosphate cells constructed with polymer electrolyte technology would eliminate leakage, further expanding the safety characteristics.  
August 2004, p. 16